Kinetics of .alpha.- and .beta.-hydrogen abstraction from ethyl chloride by bromine atoms: estimate of carbon-hydrogen bond dissociation energies and heat of formation of CH3CHCl and CH2CH2Cl radicals

1990 ◽  
Vol 94 (2) ◽  
pp. 715-717 ◽  
Author(s):  
K. Miyokawa ◽  
E. Tschuikow-Roux
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Abstraction ◽  
Heat Of Formation ◽  
Ethyl Chloride ◽  
Bond Dissociation Energies ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Kinetics Of

A study of the C 2 H 4 +HCl=C 2 H 5 Cl and C 2 H 4 +HBr=C 2 H 5 Br equilibria

1953 ◽  
Vol 216 (1126) ◽  
pp. 361-374 ◽  
Keyword(s):  
Equilibrium Constants ◽  
Entropy Change ◽  
Heat Of Formation ◽  
Ethyl Chloride ◽  
Ethyl Bromide ◽  
Bond Dissociation Energies ◽  
Kcal Mole ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Heat Of Dissociation

The equilibrium constants of the two reactions C 2 H 4 + H X = C 2 H 5 X , where X = Cl or Br, have been measured for X = Cl from 449 to 491° K, and for X = Br from 515 to 573° K, The methods of preparing and purifying the substances used, of carrying out the analyses and of determining the equilibrium constants have been described. The results for the ethyl chloride equilibrium were combined with calculations of the entropy change using Gordon & Giauque’s barrier height in ethyl chloride of 3700 cal/mole to obtain a value for the heat content change. The value for this, corrected to 298° K, is 17·1 kcal/mole. This leads to a heat of formation of ethyl chloride of – 26·7 and a heat of dissociation of the C—Cl bond in ethyl chloride of 80·9 kcal/mole. For the ethyl bromide equilibrium, the entropy change was calculated using barrier heights in ethyl bromide of 3000, 4000 and 5000 cal/mole. Using the entropy changes calculated it was concluded that the heat of reaction, corrected to 298° K, is within 0·3 kcal/mole of 19·1. This leads to a heat of formation of ethyl bromide of – 15·3 and a heat of dissociation of the C—Br bond in ethyl bromide of 67·2 kcal/mole. The two bond dissociation energies have been incorporated in the recent tables of Mortimer, Pritchard & Skinner listing such energies. The significance of the values for the bond dissociation energies in the series of RX molecules, where R = Me, Et, n-Pr, n-Bu, iso-Pr and tert.-Bu , and X = H, Cl and Br have been discussed.

Experimental methods for measurement of bond dissociation energies and heats of formation of radicals

1951 ◽  
Vol 207 (1088) ◽  
pp. 5-13 ◽  
Keyword(s):  
Experimental Methods ◽  
Experimental Results ◽  
Heats Of Formation ◽  
Bond Dissociation Energies ◽  
Carrier Gas ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Kinetics Of

The paper describes a pyrolytic method of investigating the kinetics of gaseous reactions in which toluene is used as a carrier gas. It is shown that the method is particularly suitable for the determination of bond dissociation energies. The scope of the method is illustrated by various examples. A list of bond dissociation energies obtained is given. The manner in which the experimental results obtained can be cross-checked, is indicated and illustrated by examples. The effects of various constitutional factors on the bond dissociation energies are discussed.

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